The dissected aorta .2. Differentiation of the true from the false lumen with intravascular US

PURPOSE: To determine the intravascular ultrasound (US) features of aortic dissection that can be used to differentiate the true from the false lumen. MATERIALS AND METHODS: Intravascular US and aortography were performed in 34 patients with aortic dissection. Aortic necropsy specimens were available in five patients. True and false lumina in each patient were identified on the basis of surgical, necropsy, and radiologic findings. Intravascular US studies were reviewed with attention to several local imaging features, which were evaluated for sensitivity and specificity in the differentiation of true from false lumina. RESULTS: An acute angle between the dissection flap and the outer wall of the false lumen was found in 32 patients (sensitivity, 94%; specificity, 100%). The three-layered appearance of the intact wall of true lumen and single-layered appearance of the outer wall of false lumen were seen in 33 patients (sensitivity, 97%; specificity, 100%). Cobwebs were present in the false lumen in eight patients but were not seen in the true lumen (sensitivity, 24%; specificity, 100%). Aortic thrombus was seen in the false lumen in 10 patients but was not seen in the true lumen (sensitivity, 29%; specificity, 100%). CONCLUSION: Intravascular US findings can be used to differentiate the true from the false lumen in aortic dissection.